22 ^^ig- P- Foerste 



posterior part of this area, toward the pedicel groove, is smooth 

 along the median part. The Tennessee specimens come from a 

 much lower horizon. 



Lingula modesta, Ulrich. 



(Plate II, fig. 17.) 



The type specimens of Lingula modest a were obtained from 

 the Logana bed, at Frankfort, Kentuck}^ They are distinguished 

 by their flatness, and the almost obsolete concentric striae. Speci- 

 mens occasionally attain a length of 14 mm., and a width of 9 mm. 

 In the larger specimens the lateral outline is gently convex, round- 

 ing moderately toward the beak, and more abruptly toward the 

 anterior margin. This results in a form of outline wdiich might 

 be described as quadrangular ovate, in the case of the larger 

 specimens. 



Lingula covingtonensis, Hall and Whitfield. 



(Plate V, figs. 5, 6.) 



Lingula covingtonensis (fig. 5) w'as described from that part 

 of the section at Covington, Kentucky, which lies between 25 and 

 50 feet above low water in the Ohio river. It is characterized by 

 its elliptical form, the posterior extremity, at first sight, appearing 

 almost equally rounded compared with the anterior. As a matter 

 of fact, however, the rounding is more abrupt at the beak. The 

 concentric striae are sharp and rather distant. 



Lingula cohonrgensis, as figured by Billings, is similar in form, 

 though possibly slightly more elongate. Judging from the descrip- 

 tion, the concentric striae are fine and sharply elevated on each 

 side of the beak, but more like fine concentric undulations of growth 

 elsewhere. If that be a constant feature, Lingula covingtonensis 

 differs in the sharpness of the concentric striae over the general 

 body of the shell. 



Specimens, identified as Lingula covingtonensis, occur in the 

 Logana bed, at Frankfort, Kentucky (fig. 6). They agree in out- 

 line, and are characterized by the fine, sharp, rather distant con- 

 centric striae. The shell substance is whitish. In some of the 

 specimens, the interior surface of the valves is irregularly pitted, the 

 pits being arranged approximately parallel to the concentric mark- 



